1. Field of the Invention
The present invention is directed to a bussing structure for bussing current within an electrochemical cell, wherein the bussing structure connects current collection tabs, extending from an electrode stack of the electrochemical cell, to terminals on the outside of the electrochemical cell case (which are used to connect the electrochemical cell to a desired application) such that the overall cell impedance is less than or equal to 1.5 milliohms.
2. Related Art
The related art includes electrochemical cells having electrode stacks with current collection tabs extending therefrom. The current collection tabs are connected to the bottom surface of a washer which is then riveted or otherwise connected to a terminal on the outside of the electrochemical cell, above the washer. The terminal is then used to connect the electrochemical cell to deliver electricity to a desired application. Because the current collection tabs are connected to the bottom of the washer, the connection is susceptible to shear and bending stress when the electrode stack moves within the electrochemical cell. That is, when the electrochemical cell shakes or vibrates during use, the electrode stack moves within the casing of the electrochemical cell. When the electrode stack moves, it produces forces on the current collection tabs, and thus directly on the connection between the current collection tabs and the washer. The forces produced tend to disconnect the current collection tabs from the washer, thus breaking the current path from the electrode stack to the outside of the electrochemical cell, thereby reducing or eliminating the current output from the electrochemical cell.
Additionally, the current collection tabs must be sufficiently long to enable an apparatus to be positioned between the electrode stack and the washer for connecting the tabs to the washer. Further, a plurality of tabs are at one time disposed adjacent to the bottom of the washer and are then connected thereto. Because there are many tabs it is difficult to keep them all adjacent to the washer for connection thereto. Therefore, it is difficult to ensure that all the current collection tabs are sufficiently connected to the washer. Because some tabs are not sufficiently connected to the washer, the current capacity of the electrochemical cell is decreased. Alternatively, if the tabs are connected one at a time, to ensure that they are all sufficiently connected, the process is time consuming and inefficient.